Animals, like man, have preferences for certain feedstuffs. These are either of internal origin, i.e., genetic, or of external origin, i.e., derived from habits acquired during their life cycle.
Improved palatability of animal feedstuffs will therefore play an important role in the profitability of animal husbandry.
The choice and acceptance of the feedstuff proposed to the young animal will depend firstly on the habits already acquired during its early life cycle. Thus, it will begin by going towards the place where it is used to finding its feedstuff and will tend to eat in a normal manner only if the feedstuff is identical to that to which it is already accustomed. If the nature and appearance of the feed has changed, the animal will be disorientated and, depending upon the importance of the change, will either refuse the feed completely, or upset the trough and destroy the feedstuff. All the senses of the animal are affected by this natural and instinctive reaction but, in particular, it is a combination of smell and taste which determines whether the animal will continue regular feeding.
It is known that even a few days of lowered consumption or poor assimilation can lead to a reduction in the animal's growth rate. Thus, changes in the type of feedstuff, such as those which occur during the weaning period, provoke disturbances which tend to reduce the regular feed intake and, consequently, the growth of the animals.
The most difficult period in the life of a pig is indisputably whilst it is being weaned.
During this period, the piglet is taken away from its mother and incorporated into a group of animals with which it is unfamiliar. Simultaneously, its food changes and the piglet's organism must get used to digesting something other than the sow's milk.
Effectively, the animal becomes disorientated and this leads to reduced growth for some weeks.
Pig breeders endeavour to lessen the negative effects of weaning by trying to accustom piglets to their new type of food whilst they are still with the sow. This is not easy: as long as the natural milk meets its needs, the piglet is not interested in eating anything else.
A great deal of effort has been devoted to the improvement of the feedstuff. For instance, the appetizing effects achieved by the addition of sugar, skimmed milk and rolled oats, as well as of some of the aromatic components found in the sow's milk, have been largely proved [cf. Talmadge B. Tribble, "Feed Flavor and Animal Nutrition," 1st Ed., Agriaids, Inc. (1962)].
However, it has been noticed that piglets not only ate the food they liked, but also played with it and thus wasted it.
Moreover, although successful liquid sow milk substitutes have been developed, they are not accepted by the farm operators due to the fact that they must be prepared daily and fed at constant temperature. Another disadvantge is that all feeding equipment must be thoroughly cleaned and extreme sanitation maintained.